This invention relates to apparatus for drilling holes in sheet material such as, for example, sheets of flexible textile or plastic material used in the garment or upholstery industry, and deals more particularly with such a drilling apparatus for use in an automatically controlled machine wherein the drill and sheet material are moved relative to one another to allow the cutting of holes at various locations on the sheet material.
Although not so limited, the drilling apparatus of this invention has particular utility when used, as herein described, in association with an automatic machine for cutting cloth or other sheet material such as shown in U.S. patent application Ser. No. 06/861,148, and entitled Cutter Head and Knife for Cutting Sheet Material, wherein the drilling apparatus is attached to a work carriage movable in two coordinate directions over a sheet of sheet material, or over a lay-up of sheets of sheet material, spread on a supporting surface with the work carriage supporting a cutter for cutting the sheet material along lines of cut to produce pattern pieces used subsequently in making garments or other articles. The drilling apparatus is used alternately with the cutter to drill holes for marking or other purposes in the sheet material.
A drilling apparatus of the general type in question is shown by U.S. Pat. No. 3,730,634. As there disclosed the drilling apparatus includes an elongated hollow drill having a sharpened free lower end. In a drilling operation the drill is rotated about its central axis and moved downwardly through the sheet material so that the sharpened edge removes material, in the form of plugs or chips, which enters the central bore of the drill. Inwardly of the cutting edge the bore of the drill widens so that after the removed material passes a short distance from the cutting edge it enters an enlarged section of the bore at which it loses tight contact with the bore wall, thereby allowing it to move freely to and thru a lateral escape port.
The type of drill described in U.S. Pat. No. 3,730,634 has several disadvantages. Among these is the fact that the widening of the drill bore inwardly of the cutting edge requires that the drill have either a relatively thick wall or a bulbous outer profile giving the drill a maximum outer diameter considerably larger than the diameter of the hole cut in the material, this making it difficult for the drill to penetrate the material being cut, such difficulty being especially pronounced in the case of drilling a dense material such as tightly woven textiles or plastics. Another disadvantage is that the drills are relatively expensive to manufacture and have a relatively limited service life since they can only be shortened a small amount by sharpening before reaching the widened portion of the bore and becoming out of size.
An aim of the present invention is therefore to provide a sheet material drilling apparatus of the foregoing character using a drill which is easy and economical to manufacture, and which has a maximum outside diameter only slightly larger than the diameter of the hole to be cut so that the drill may pass readily thru the work material being cut.
A further object of the invention is to provide such a drilling apparatus including a means for positively driving or cleaning the removed material from the drill bore after each drilling operation to prevent the drill from becoming inoperative through the clogging of its bore.
A still further object of the invention is to provide a drilling apparatus of the foregoing character which is relatively light in weight yet powerful so as to adapt it for mounting to the work carriage of a high speed sheet material cutter of the type shown for example by the aforesaid U.S. patent application Ser. No. 06/861,148.
Another object of the invention is to provide a drilling apparatus having a pressure fluid motor for rotating the drill and a pressure fluid actuator for moving the drill into drilling relationship with the work material, and which motor and actuator are energized simultantously at the beginning of and during a drilling operation from a common pressurized fluid supply line.
Other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment and from the accompanying drawings and claims.